[Radiation-induced neuropathies: collateral damage of improved cancer prognosis]

Pain hypersensitivity, sensorimotor impairment, and decreased muscle force in a novel rat model of radiation-induced peripheral neuropathy

INTRODUCTION

Radiation-induced peripheral neuropathy is a rare, but serious complication often resulting in profound morbidity, life-long disability, and chronic debilitating pain. Unfortunately, this type of peripheral neuropathy is usually progressive, and almost always irreversible. To date, a standardized rat model of radiation-induced peripheral neuropathy has not been established. The purpose of the present study was to examine neuropathic pain, sensorimotor impairment, and muscle force parameters following the administration of a clinically relevant radiation dose in a rat model.

METHODS

Ten rats were randomly assigned to one of two experimental groups: (1) radiation and (2) sham-radiated controls. Radiated animals were given a clinically relevant dose of 35 Gray (Gy) divided into five daily doses of 7 Gy/day. This regimen represents a human equivalent dose of 70 Gy, approximating the same dosage utilized for radiotherapy in oncologic patients. Sham-radiated controls were anesthetized and placed in the radiation apparatus but were not given radiation. All animals were tested for baseline values in both sensorimotor and pain behavioral tests. Sensorimotor testing consisted of the evaluation of walking tracks with the calculation of the Sciatic Functional Index (SFI). Pain-related behavioral measures consisted of mechanical allodynia (von Frey test), cold allodynia (Acetone test), and thermal allodynia (Hargreaves test). Animals were tested serially over an 8-week period. At the study endpoint, electrophysiological and muscle force assessments were completed, and histomorphometric analysis was performed on all sciatic nerves.

RESULTS

Animals that underwent radiation treatment displayed significantly greater pain hypersensitivity to mechanical stimulation as compared to sham radiated controls from weeks 4 to 8 of testing. SFI values indicated sensorimotor impairments in the overground gait of radiated animals as compared to non-radiated animals. Furthermore, radiated animals displayed reduced twitch and tetanic muscle force when compared to sham radiated controls.

CONCLUSIONS

A clinically relevant human equivalent dose of fractionated 35 Gy in rats established significant pain hypersensitivity, impairments in sensorimotor locomotion, and decreased muscle force capacity. This novel rodent model of radiation-induced peripheral neuropathy can be utilized to assess the potential efficacy of therapeutic treatments to either prevent or remediate this clinically debilitating condition.

Predictive factors for persistent and late radiation complications in breast cancer survivors

PURPOSE

With improved diagnostic techniques and treatments of breast cancer, overall survival times are longer, giving more opportunity for normal tissue complications of treatment to manifest. Radiation late effects (RLEs) could have profound long-term impacts on the quality of life of the survivors. The aim of this study was to identify predictive factors influencing timing and types of complications in patients referred to the Adult Radiation Late Effects Clinic (ARLEC).

METHODS

In a period of 16 years, 296 breast cancer patients were referred to the ARLEC. The clinical records were retrospectively studied to collect epidemiologic, medical and treatment data. Associations were sought between candidate predictive factors and time to the first complication after radiation treatment (RT) completion (primary outcome), and pain or swelling (secondary outcomes) using univariable and multivariable linear and logistic regression analyses. All analyses were performed in SAS, version 9.4.

RESULTS

All patients were female with a mean age of 56.3 years. The first treatment-related complication occurred after a median of 3 months. Patients were followed at ARLEC for a median of 18 months. Older age and delay from surgery to RT (S-RT delay) were associated with earlier onset of complications (both p < 0.001). The most common complications were breast pain (62.1%) and swelling (45.9%). Histology and RT boost were associated with pain (p = 0.035 and 0.013). RT boost and S-RT delay on the other hand were associated with swelling (p = 0.013 and 0.005).

CONCLUSIONS

Clinical factors identified could help recognize the patients at high risk for developing RLEs and alert physicians to initiate earlier diagnostic and therapeutic measures.

Effect of BioZorb® surgical marker placement on post-operative radiation boost target volume

Objective

BioZorb® is a tumor bed marker placed during partial mastectomy for targeted post-operative radiation. This study was designed to evaluate BioZorb® effect on radiation boost clinical target volume (CTV), planning target volume (PTV), median dose to ipsilateral lung (Gy), and heart irradiation in left-sided cancers.

Methods

Data was collected via a retrospective cohort study with two study arms: BioZorb® intra-operative placement versus no BioZorb® placement. Patients were stratified by BMI, age, tumor laterality and volume, and cancer stage. Mean, standard deviation, median, range of cubic centimeters of clinical and planning target volume, cardiac dose in left-sided cancers, ipsilateral lung dose, and volume of ipsilateral lung receiving 20 Gy were reported.

Results

Of 143 patients, median CTV (cm³) was 8.7 and 14.2 (P = 0.0048), median PTV (cm³) was 53.2 and 79.6 (P = 0.0010), median ipsilateral lung Gy was 7.53 and 6.74 (P = 0.0099) and volume (cc) of ipsilateral radiation lung at 20 Gy was 13.4 and 12 (P = 0.008), and median heart Gy in left-sided cancers was 2.01 and 2.21 (P = 0.9952) in BioZorb® and non-BioZorb® arms, respectively. Patients with BMIs of 25–30 had CTV medians of 7.8 and 11.1 in BioZorb® and non-BioZorb® arms, respectively (P = 0.0293).

Conclusion

The BioZorb® arm showed statistically significant reductions in CTV and PTV but not ipsilateral lung or heart irradiation.

Neuromuscular complications in cancer

Cancer is becoming a treatable and even often curable disease. The neuromuscular system can be affected by direct tumor invasion or metastasis, neuroendocrine, metabolic, dysimmune/inflammatory, infections and toxic as well as paraneoplastic conditions. Due to the nature of cancer treatment, which frequently is based on a DNA damaging mechanism, treatment related toxic side effects are frequent and the correct identification of the causative mechanism is necessary to initiate the proper treatment. The peripheral nervous system is conventionally divided into nerve roots, the proximal nerves and plexus, the peripheral nerves (mono- and polyneuropathies), the site of neuromuscular transmission and muscle. This review is based on the anatomic distribution of the peripheral nervous system, divided into cranial nerves (CN), motor neuron (MND), nerve roots, plexus, peripheral nerve, the neuromuscular junction and muscle. The various etiologies of neuromuscular complications - neoplastic, surgical and mechanic, toxic, metabolic, endocrine, and paraneoplastic/immune - are discussed separately for each part of the peripheral nervous system.

Clinical and neurophysiological evaluation of persistent sensory disturbances in breast cancer women after mastectomy with or without radiotherapy

PURPOSE

Breast cancer surgery or radiotherapy (RT) are potential causes of persistent pain syndrome. It remains to be clarified whether numbness or pain reported by patients after mastectomy and RT are conditioned by changes in nerve transmission. The aim of this study was to examine the potential relationship between subjective sensory complications and neurophysiological examinations in breast cancer survivors with post-mastectomy pain syndrome.

METHODS

Sixty breast cancer survivors (30 patients only after mastectomy - group A; and 30 after mastectomy with RT - group B) complaining of pain and sensory disturbances in the brachial plexus area and 20 healthy women (group C) were studied with regard to sensory perception and pain intensity using the Visual Analogue Scale and electroneurography (ENG).

RESULTS

There was a statistically significant decrease in the amplitudes in SCV recordings following stimulation of the ulnar (p = 0.04) and lateral cutaneous antebrachii nerves (p = 0.02) in group B in comparison to group C. Additionally, a significant decrease in the amplitude and conduction velocity parameters was detected in the sensory fibers of the median and medial cutaneous antebrachii nerves in group A (p = 0.00 and p = 0.02, respectively) in comparison to group C.

CONCLUSIONS

The results of this pilot study suggest persistent post-mastectomy pain syndrome sometimes appears as a result of nerve injury in course of breast cancer surgery and RT. Therefore studies in nerve conduction may be added to the comprehensive patient assessment used in planning breast cancer patients' rehabilitation after oncological treatment has finished.

Clinical observation of peripheral nerve injury in 2 patients with cancer after radiotherapy

Aim of the study

This study aims to analyze the clinical manifestations and sequelae of peripheral nerve radiation damage of two cases of cancer patients after radiotherapy at the corresponding sites in clinical practice and to summarize experiences and lesions in order to provide a reference for future tumor radiotherapy.

Material and methods

Some data of two cases of patients, such as doses of radiotherapy, clinical manifestations and damage occurrence time, were collected and examinations were conducted to define diagnosis. Afterwards, therapies and follow-up were conducted.

Results

Case 1 (rectal cancer) was diagnosed as mild left lower extremity nerve damage. After the symptomatic treatment, the disease condition was improved, and there was no tumor recurrence sign. Case 2 (breast cancer) was diagnosed as left brachial plexus damage, and left upper extremity movement function was lost completely. While the analgesic treatment was conducted, anti-tumor relevant treatments were being carried out.

Conclusions

Radiotherapy can cause different extents of radioactive nerve damage. In practice, it is necessary to constantly improve the radiotherapy technology level and actively prevent the occurrence of complications. Once symptoms appear, the diagnosis and treatment should be conducted as early as possible in order to avoid aggravating damage to cause dysfunction and cause lifetime pain to patients.